Summary Air Canada Regional Airlines Flight8610 (TCN8610), a FokkerF-28MK1000 aircraft (C-FCRK), serial number11087, was on a scheduled IFR, night passenger flight from Toronto/ LesterB. Pearson International Airport, Ontario, to Saint John, New Brunswick. On board were 4crew members and 51passengers. The en route portion of the flight was uneventful and, at 0030 Atlantic standard time, the aircraft landed on the centreline of Runway05 at SaintJohn. After the nosewheel touched down, the aircraft started to drift uncontrollably to the left and the left main wheels went off the side of the runway for approximately 900feet before regaining the runway surface. The left main gear track was 15feet from the runway edge at its furthest point. Aircraft damage was limited to minor cuts in the tires of the right main gear and the nosewheel. There were no injuries to the passengers or crew. Ce rapport est galement disponible en franais. Other Factual Information Saint John Airport is a certified, uncontrolled airport. The airport has two runways; Runway05/23, which is 7000feet long, and Runway4/32, which is 5100feet long. Both are 200feet wide and asphalt surfaced. At 0006 Atlantic standard time,1 Air Canada Regional Airlines Flight8610 (TCN8610) checked in with the SaintJohn Flight Service Station (FSS), reported that they were estimating arrival at approximately 0030, and requested airfield information for SaintJohn. The FSS specialist advised that the weather at Saint John was as follows: visibility mile in light snow; precipitation ceiling at 800feet; winds from 140degrees magnetic at nine knots; temperature -2C; dew point -5C; and altimeter setting 30.38. The airfield was snow covered and a runway surface condition (RSC) report was being prepared; however, the report was not yet available. Saint John FSS records indicate that it had started snowing at 2308. The temperature had been fluctuating slightly above and below the freezing point in the hours prior to the snowfall; at 2300, the temperature was 0.1C. Prior to this snowfall, there had been no precipitation for days and both runways had been 100per cent bare and dry. Airfield snow removal personnel, off shift at 2300hours, had departed the airfield. They were recalled shortly after the snowfall commenced. At 0012, airfield maintenance staff reported to the FSS that the RSC for Runway 05/23 was 100percent snow covered up to inch. The Canadian Runway Friction Index (CRFI)2 was measured and the average reading obtained for the runway was 0.52. This value is equated with good friction characteristics, approximately equivalent to a wet runway covered with 0.02inches of water. The RSC report was passed to the FSS specialist who, in turn, attempted to relay it to TCN8610; however, the crew was no longer monitoring the Saint John radio frequency. At 0019, snow removal vehicles were available to start sweeping operations, but because the aircraft was expected to land at 0030, the vehicles were told to remain clear of the landing runway. At 0020, TCN8610 switched to the Saint John FSS frequency and advised FSS that they were 21miles back, out of 10000feet, and would be conducting an ILS approach via the 17DME arc to Runway05. The FSS specialist acknowledged the radio transmission and passed the RSC report for Runway05 to the flight. The specialist also advised that the sweepers were prepared for a centreline sweep and the time required for the sweep would be 11to 13minutes. The crew declined the offer of a centreline sweep of the runway. At about 0022, airfield maintenance reported to the FSS specialist that the non-landing runway (Runway14/32) was 100percent snow covered to a depth of inch, with a CRFI of0.23. This information was not passed to TCN8610, and the crew did not ask for an update of the CRFI before landing. Snow removal vehicles then commenced clearing Runway14/32. The aircraft flew an uneventful ILS approach with a landing reference speed (Vref) speed of 117knots indicated airspeed (KIAS). Flap42 was used for the approach and landing. Flight data recorder information showed that the aircraft touched down near the centreline at 0030, at a speed of about 114KIAS, and on a heading of 054degrees (three degrees right of runway heading). The nosewheel touched about two seconds later at 106KIAS. After nosewheel contact, the aircraft heading increased to 065degrees, while the aircraft drifted toward the left side of the runway. The drift was likely due to the combined effect of the crosswind and a small amount of pre-existing left drift at touchdown. However, the extent to which either contributed to the drift could not be established. The crew attempted to correct the ground path of the aircraft by using rudder and nosewheel steering inputs; however, the aircraft continued to drift toward the left and off the runway, despite the increased heading to the right. The left main wheels were off the runway edge for about 900feet, the furthest point of excursion being 15feet. The aircraft was slewed 15to 20degrees right of the runway heading, with the right main gear tracking in about the same path as the nosewheel during the excursion. Partial control of the aircraft was regained as the left main wheels returned to the runway surface. Steering response was still ineffective, and the aircraft continued sliding with the nose slewed to the right as it approached the runway centreline. The crew shut down the left engine at about 60KIAS and the aircraft aligned with the runway. They brought the aircraft to a stop then taxied to the ramp. During the taxi, the crew advised the FSS specialist that the braking action on Runway05 was very poor and that they believed the aircraft had come very close to the runway edge. After the occurrence, ground personnel confirmed that the aircraft had slid off the runway edge. Both runways were cleared, and a subsequent RSC report indicated that there was 1/8inch of slush contamination on the cleared centre 100-foot portion. Although a CRFI is not normally done with slush, a measurement is taken whenever a runway excursion occurs. The CRFI for the cleared portion of Runway05/23 was0.36; for Runway14/32, it was0.34. The aircraft did not leave any significant tire skid marks on the runway surface. After the flight, the crew inspected the aircraft for damage, consulted with company maintenance personnel in Toronto, and then re-inspected the aircraft the following morning. No damage was apparent, and the aircraft departed SaintJohn for passenger revenue flights to Toronto, Fredericton, and Toronto. After the aircraft departed for Fredericton, it was discovered that the aircraft tires had struck a runway edge light. Because of snow cover, the broken light had not been noticed immediately after the occurrence. When the aircraft landed at Toronto, small cuts, normally associated with operations from gravel runways, were noted in the right main tires and the tires of the nosewheel. Although the cuts were not sufficient to render the tires unserviceable, the operator replaced them as a precaution. The aircraft braking and steering functioned normally. Surface conditions have a great influence on the friction characteristics of the runway. Poor friction characteristics will lead to both decreased stopping and steering performance. RSC/CRFI reports are a snapshot of runway conditions that exist at the time of the observation. They do not indicate if a contaminant is accumulating, the rate of accumulation, whether melting or freezing is ongoing, or other factors that would help crews to decide on the suitability of the runway for landing. Transport Canada's Aerodrome Safety Circular (ASC)2000-002 entitled Aircraft Movement Surface Condition Reporting (AMSCR) for Winter Operations describes conditions when RSC reports are required. The ASC states the following: there is frost, snow, slush or ice on a runway, a taxiway or an apron; there are snow banks, drifts or windrows adjacent to a runway, a taxiway or an apron; sand, aggregate material, anti-icing or de-icing chemicals are applied to a runway, a taxiway or an apron; whenever the cleared runway width falls below full width; whenever there is a significant change in runway surface conditions; following any aircraft accident or incident on a runway, taxiway or apron. there is frost, snow, slush or ice on a runway, a taxiway or an apron; there are snow banks, drifts or windrows adjacent to a runway, a taxiway or an apron; sand, aggregate material, anti-icing or de-icing chemicals are applied to a runway, a taxiway or an apron; whenever the cleared runway width falls below full width; whenever there is a significant change in runway surface conditions; following any aircraft accident or incident on a runway, taxiway or apron. Revisions to RSC reports are required when there is a significantchange in surface conditions; however, the meaning of this term is not clearly defined by the ASC. CRFI measurements are accurate only for packed snow or ice. For this reason, measurements are not taken when there is a layer of slush on the runway surface with no other type of contamination condition present. When a CRFI reading is not available, crews can refer to the Runway Surface Condition and CRFI equivalent chart found in the A.I.P. Canada. Using this chart, crews can determine a CRFI equivalent from among typical runway surface contaminants such as water, snow, or ice. This chart does not, however, have a CRFI equivalence value for slush contamination. Without either a CRFI measurement or a CRFI equivalence value for slush, crews do not have a standard means of estimating the effect of the slush on stopping performance, and consequently, must use their best judgement as to the suitability of the runway for landing. The A.I.P. Canada also contains a crosswind limits table for various CRFI readings. The chart shows that the recommended minimum CRFI for the crosswind, which was 90degrees at 9knots, was0.3. Landing with a CRFI below this minimum value could result in uncontrollable drifting and yawing. The crew had received a CRFI reading of0.52, well above the recommended minimum CRFI. The ICAO Airport Services Manual states the following: Before giving detailed consideration to the need for, and methods of, assessing runway surface friction, or the drag effect due to the presence of meteorological contaminants such as snow, slush, ice or water, it cannot be over-emphasized that the goal of the airport authority should be the removal of all contaminants as rapidly and completely as possible and elimination of any other conditions on the runway surface which adversely affect aeroplane performance. In considering the relative merits of measuring the friction coefficient on a compacted snow- and/or ice-covered runway, compared with effective measures to maintain a surface free of any contaminants at all times, it should be noted that immediate removal of snow and ice should receive the highest priority.